vector::size und vector::capacity
Veranschaulicht, wie die Features Vektor::Größe und Vektor::Kapazität Standardvorlagenbibliothek (STL) in Visual C++ verwendet.
template<class _TYPE, class _A>
void vector::reserve(
size_type _N
);
template<class _TYPE, class _A>
size_type vector::max_size( ) const;
template<class _TYPE, class _A>
void vector::resize(
size_type _N,
_TYPE _X = _TYPE( )
);
template<class _TYPE, class _A>
size_type vector::capacity( ) const;
template<class _TYPE, class _A>
size_type vector::size( ) const;
Hinweise
.gif "Hinweis") Hinweis |
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Die Klasse/Parameternamen im Prototyp stimmen nicht mit der Version in der Headerdatei ab.Einige wurden geändert, um die Lesbarkeit zu verbessern. |
Das Beispiel deklariert einen leeren Vektor von ganzen Zahlen.Er fügt ein einzelnes ganzzahliges Element dem Vektor hinzu und zeigt dann Informationen über die Größe des Vektors, maximale Größe und die Kapazität auf.Es reserviert Speicher für 1,000 Elemente und zeigt die gleichen Informationen über den Vektor an.Schließlich ändert er den Vektor zu 2,000 Elementen Größe und zeigt dann die Informationen an.
Beispiel
// Remax.cpp
// compile with: /EHsc
// Illustrates vector::reserve, vector::max_size,
// vector::resize, vector::resize, and vector::capacity.
//
// Functions:
//
// vector::max_size - Returns maximum number of elements vector could
// hold.
//
// vector::capacity - Returns number of elements for which memory has
// been allocated.
//
// vector::size - Returns number of elements in the vector.
//
// vector::resize - Reallocates memory for vector, preserves its
// contents if new size is larger than existing size.
//
// vector::reserve - Allocates elements for vector to ensure a minimum
// size, preserving its contents if the new size is
// larger than existing size.
//
// vector::push_back - Appends (inserts) an element to the end of a
// vector, allocating memory for it if necessary.
//
//////////////////////////////////////////////////////////////////////
// The debugger cannot handle symbols more than 255 characters long.
// STL often creates symbols longer than that.
// When symbols are longer than 255 characters, the warning is disabled.
#pragma warning(disable:4786)
#include <iostream>
#include <vector>
using namespace std ;
typedef vector<int> INTVECTOR;
int main()
{
// Dynamically allocated vector begins with 0 elements.
INTVECTOR theVector;
// Add one element to the end of the vector, an int with the value 42.
theVector.push_back(42) ;
// Show statistics about vector.
cout << "theVector's size is: " << theVector.size() << endl;
cout << "theVector's maximum size is: " << theVector.max_size()
<< endl;
cout << "theVector's capacity is: " << theVector.capacity() << endl;
// Ensure there's room for at least 1000 elements.
theVector.reserve(1000);
cout << endl << "After reserving storage for 1000 elements:" << endl;
cout << "theVector's size is: " << theVector.size() << endl;
cout << "theVector's maximum size is: " << theVector.max_size()
<< endl;
cout << "theVector's capacity is: " << theVector.capacity() << endl;
// Ensure there's room for at least 2000 elements.
theVector.resize(2000);
cout << endl << "After resizing storage to 2000 elements:" << endl;
cout << "theVector's size is: " << theVector.size() << endl;
cout << "theVector's maximum size is: " << theVector.max_size()
<< endl;
cout << "theVector's capacity is: " << theVector.capacity() << endl;
}
Beispielausgabe
Die folgende Ausgabe wird für x86-, oder legt diesen fest.
theVector's size is: 1
theVector's maximum size is: 1073741823
theVector's capacity is: 1
After reserving storage for 1000 elements:
theVector's size is: 1
theVector's maximum size is: 1073741823
theVector's capacity is: 1000
After resizing storage to 2000 elements:
theVector's size is: 2000
theVector's maximum size is: 1073741823
theVector's capacity is: 2000
Anforderungen
Header: <vector>